30 Questions
What is the relationship between the intensity of illumination and the distance from a point source?
I ∝ 1/r^2
According to the principle of photometry, what is the relationship between L1 and L2 when I1 = I2?
L1^2 r1^2 = L2^2 r2^2
What is the unit of illuminance?
Lumen per square meter
What happens to the velocity, wavelength, and frequency of light after reflection?
Only intensity decreases
What is the relationship between luminous intensity and illuminance?
I ∝ L
What happens to a light ray when it goes from a rarer medium to a denser medium?
It bends towards the normal
What is the relationship between the angle of incidence and the angle of refraction according to Snell's law?
The ratio of the sine of the angle of incidence to the angle of refraction is a constant
What is the effect of temperature on the refractive index of a medium?
It decreases the refractive index
What is the relationship between the wavelength of light and its refractive index?
Longer wavelengths have a lower refractive index
What is the direction of deviation of a light ray when it goes from a denser medium to a rarer medium?
Away from the normal
What happens when two lenses of equal focal length but of opposite nature are in contact?
The combination behaves as a plane glass plate
What is the relationship between the focal length of a lens and its power?
The power of a lens decreases as its focal length increases
What is chromatic aberration?
The image of a white object appearing coloured and blurred due to the different refractive indices of the lens for different colours
What is the formula for the focal length of a combination of lenses?
F = 1 / (1/f1 + 1/f2)
What is the relationship between the refractive indices of the glass and the lens, μg and μl, when the focal length of the lens is greater than the focal length of the air?
μg > μl
What is the relationship between the resolving power and the aperture of an objective?
Resolving power is directly proportional to the aperture.
What type of lens is used in a binocular to provide an erect image?
Totally reflecting prism
What is the advantage of using a reflecting telescope over a refracting telescope?
Reflecting telescopes are less prone to chromatic aberration.
What is the purpose of the objective in a telescope?
To collect and focus light from the object
What is the advantage of binocular vision?
It allows for the perception of depth and a three-dimensional image
What happens to the magnification of a telescope when the field and eye lenses are interchanged?
It becomes reciprocal of its initial value
Why are lens doublets in telescopes achromatic for blue and red colours?
Because the human eye is most sensitive between blue and red colours
What is the effect of increasing the aperture of the objective lens in a telescope?
It increases the resolving power of the telescope
What is the effect of using a composite lens in a telescope?
It increases aberrations and increases brightness
What happens to the magnification of a telescope as the length of the tube increases?
It decreases
What is the condition for an object and final image to be at infinity in a telescope?
f = o = fe
What is the purpose of using a parrot on the objective of a large telescope?
To reduce the aperture of the objective
What is the unit of luminous flux if monochromatic light of wavelength 5500 Å is 1 lumen?
Lumen
Which lenses would be chosen for a good telescope and microscope respectively?
f1 (o), f4 (e) and f4 (o), f3 (e)
What is the relationship between the luminous flux R and the luminous intensity Φ of a source?
R ∝ Φ
Assess your understanding of illumination and photometry concepts, including intensity of illumination, point sources, line sources, and parallel beams of light.
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